The recent successes using islet cell transplantation have demonstrated that cell replacement therapy has the potential to be a viable treatment for type 1 diabetes. However, for cell replacement therapy to be broadly applied will require that several obstacles be overcome. Two of these are: (i) the supply of cells available for transplantation, and (ii) development of means to enhance the engraftment and function of transplanted cells through the creation of a platform and extra-hepatic site for the transplantation of insulin- secreting cells. The goal of this proposal is to develop means of overcoming these obstacles. To accomplish this, we have formed a multidisciplinary team of investigators with expertise in stem cell biology, diabetes, islet transplantation, bioengineering and materials science, and imaging. This multidisciplinary research team will develop approaches using scaffold technologies to enhance the engraftment and function of transplanted human embryonic stem cells (hESCs) and of differentiating them into insulin-secreting cells. They will accomplish this by addressing the hypothesis that microporous scaffolds capable of controlled delivery of peptides and co-transplantation of endothelial cells can be used to create a microenvironment that will promote the differentiation of hESCs into insulin-secreting cells and support the transplantation and engraftment of insulin-secreting cells into extra-hepatic sites. The specific aims for this study are as follows. (1) To develop an optimal approach to cell-based therapies for diabetes that can be applied to differentiated hESCs using mature human islets as a model system. Human islets seeded onto microporous scaffolds will be transplanted into NOD-SCID mice with streptozotocin-induced diabetes. The impact of controlled delivery of angiogenic peptides and co-transplantation of endothelial cells on islet survival and vascularization and the ability of the islets to correct hyperglycemia will be assessed. (2) To use scaffold technologies to create a microenvironment to optimize the transplantation and engraftment of hESCs. hESCs differentiated in embryoid bodies will be seeded onto synthetic scaffolds and transplanted into mice. The ability of the scaffold to impact the vascularization and survival of cells will be assessed via histochemistry and fate- mapping using novel magnetic resonance imaging techniques. (3) To develop means to differentiate hESCs into insulin-secreting cells. Modulation of culture conditions and exposureto a microenvironment created by the synthetic scaffolds will be used to develop means of generating insulin-secreting cells from hESCs. The ability of the differentiated hESCs to correct hyperglycemia will be tested by transplanting them on scaffolds into murine models of diabetes. Approaches established in Aims 1 and 2 will be used to help direct the transplantation studies. Successful completion of the proposed studies will leave us poised to translate these studies into non-human primates and subsequently humans.